The growth of thin films on substrates by heteroepitaxy is an important manufacturing step in the semiconductor technology. For instance, in the field of light-emitting semiconductor devices or solar cells, there is a need to grow heteroepitaxial films on substrates as sapphire or SiC to form a final semiconductor device. After transfer of the heteroepitaxial films to another substrate, these films can, for instance, be used for epitaxial growth of layers used in electronic and opto-electronic applications.
However, when films are formed by heteroepitaxy on substrates with different lattice constants and different coefficients of thermal expansion as compared to the ones of the films, detrimental effects on material quality of layers grown on the films are caused by compressive/tensile strain and the corresponding generation of defects like dislocations, cracks, plastic relaxation, etc., that result in detrimental effects on the material quality of layers grown thereon.
Thus, in the art, compliant layers, e.g., low-viscosity layers, have been provided between the heteroepitaxial film and a target substrate in order to release the strains by heat treatment.
Presently used methods for the relaxation of strained heteroepitaxial films, however, often do not show satisfying results with respect to the suppression of buckling, etc. Moreover, the transfer of heteroepitaxial films grown on a seed (growth) substrate, including some seed layer to another substrate that is to be used for the further manufacture of a particular semiconductor, raises the problem of maintaining the heteroepitaxial films intact, in general, and, in particular, removing the seed substrate without damaging the heteroepitaxial films.
Therefore, it is a problem underlying the present invention to provide a method for the formation of reliably relaxed and intact material layers (islands) that can suitably be used for the manufacture of a semiconductor device.